Duo Apps

Guide

iPhone Duo app compatibility, explained

Every iPhone app runs on the iPhone Duo, but not every app is built for its foldable 7.6-inch inner display yet. Here’s how to tell which apps are, and what happens to the rest.

Updated

Do all iPhone apps work on the iPhone Duo?

Yes, iPhone apps run on the iPhone Duo. What varies is how well they use it. Apps optimized for the iPhone Duo fill the inner display and adapt as you fold and unfold the phone. Apps that haven’t been updated still open and work, but don’t make full use of the larger screen (MacTech, Oct 22 2026).

How to check if an app is optimized for iPhone Duo

Look for the Made for iPhone Duo badge on the app’s App Store page. Apple says apps optimized for iPhone Duo “are easy to identify with a Made for iPhone Duo badge on product pages across the storefront” (Apple Newsroom, Oct 22 2026).

You can also search the Duo Apps list: every app shows its grade out of 10, which features work, and the sources behind it.

What happens to apps that aren’t optimized?

They work, but they don’t fill the inner display. Launch-week reports describe three levels (PhoneArena, MacTech, Oct 22 2026):

  • Not updated for iOS 27: the app runs in a smaller window with black borders around it.
  • Updated for iOS 27: the app is resized to fill more of the screen, but still sits inside a border.
  • Optimized with the iOS 27.1 SDK: the app uses the whole inner display.

Apple’s own announcements describe optimized apps but don’t document these levels.

Why do some apps show black borders on the iPhone Duo?

Black borders mean the app hasn’t been optimized for the iPhone Duo yet. Nothing is wrong with your phone or its settings: only the developer can fix it, by updating the app.

When will my app be optimized?

That’s up to each developer. Apple’s tools for adapting apps come with the iOS 27.1 SDK, and developers can submit optimized apps to the App Store now (Apple Newsroom, Oct 22 2026). Where Apple or the developer has given a date, the Coming to iPhone Duo list shows it.

Can apps use both displays at once?

Yes. With what Apple calls scene accessories, apps can show content on the inner and outer displays at the same time. Apple’s example is a teleprompter (Apple Newsroom, Oct 22 2026).

The iPhone Duo’s two displays

  • Inner display: 7.6 inches (7.58 inches diagonally), foldable.
  • Outer display: 5.4 inches (5.36 inches diagonally).

Source: Apple Newsroom, Sep 9 2026.